High resolution measurement of coercivity variations in magneto-optical recording media

The coercivity of amorphous rare-earth-transition-metal magnetooptical recording media has been measured as a function of position on the films utilizing a micro-Kerr-hysteresis-loop tracer with an effective measuring aperture of 0.5 mu m. The local variations of wall motion coercivity (H/sub c/) in films whose magnetization reversal was dominated by nucleation were as large as 20%. In contrast, H/sub c/ in films whose magnetization reversal was dominated by domain-wall motion exhibited a negligibly small variation from place to place. It was found that the fields required to collapse micron-sized domains were typically 20% less than H/sub c/ as measured above. The predominant magnetization-reversal mechanism in the films is mainly determined by fabrication processes.<
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